1. Field of the Invention
A gimbal is used to support a seismic detector, such as a geophone, to give it free limited angular movement with a single degree of freedom in one direction about a horizontal axis.
2. Description of the Prior Art
In seismic prospecting, spread cables are used to interconnect strings of geophone transducers to seismic recording instruments. The geophone is mounted in a casing which is implanted into the earth to allow the geophone to detect returned seismic waves. Normally, geophones are planted upright so that they can detect only vertical earth motion. In recent years the need arose to record horizontal seismic waves as well and with geophones which are positioned horizontally instead of upright.
To plant a geophone so that its axis is substantially parallel to the horizontal is not an easy task. Conventionally, this is accomplished by outfitting each transducer with a level indicator which allows the operator to keep adusting the geophone planting until the axis of the geophone is approximately horizontal. Unfortunately, such a procedure is very time-consuming when considering that a seismic crew intending to detect horizontal waves normally utilizes several thousand of such horizontal geophone transducers.
The main object of the present invention is to eliminate the need of a level detector for each geophone transducer as well as to reduce substantially the cost of the labor associated with the present procedure for planting horizontal geophone transducers.